There is a pressing need for rapid and portable detection for neurotoxins, and though there has been considerable research in this field, there are very few sensors available to monitor an individual's exposure that can be produced and deployed on a large scale. In addition to monitoring of facilities, evaluation of individual exposure for those potentially exposed to neurotoxins, including farmers, first responders during a biochemical attack, and military personnel in at-risk areas, is a key issue for current biosensing technology.
A plethora of analytical methods are available to detect and quantitate neurotoxins. Neurotoxin quantitative analysis can be performed by detecting the products of toxin-specific enzymatic degradation or reaction with a toxin-specific reagent. (Enserink, M. Science, 2001, 294, 1266).
Alternative methods include monoclonal antibodies to detect a specific antigen by fluorescence visualization (Ong, et al., Analytica Chimica Acta, 2001, 444, 143), or monitor conformational changes in the antibody that occur as a result of antigen binding. (Goldman, et al., Anal. Chem. 2004, 76, 684). Monitoring conformational changes in antibody, however, requires high degree of specificity.
Fluorescence resonance energy transfer (FRET) can be an ideal method for monitoring changes in protein conformation because the effect is highly distance-dependent. (Haugland, R. P. Handbook of Fluorescent Probes and Research Products, Ninth Edition; Molecular Probes: Eugene, Oreg., 2002). FRET is a process that can occur between a donor-acceptor pair of fluorophores in which one fluorophore, when excited, transfers some of its energy without emitting light to a second fluorophore whose absorption wavelength overlaps the emission of the donor. FRET also depends on the quantum yield, relative donor-acceptor dipole orientations, and the ratio of FRET donors to acceptors.
Over the past years, organic dyes have been used extensively in FRET applications, but the requirements of FRET make matching a donor-acceptor pair difficult. (Lakowicz, J. R. Principles of Fluorescence Spectroscopy, 2nd ed.; Kluwer Academic: New York, 1999).
Many available methods of detecting neurotoxins are neurotoxin-specific. In situations at risks, there is a need for a universal neurotoxin detector. It is known that nearly all neurotoxins act on the acetylcholinesterase enzyme (AChE). Using such property of AChE, sensors based on the detection of AChE-catalyzed hydrolysis products are currently in development. Nevertheless, these methods rely on cumbersome and extensive instrumentation. (Pardo-Yissar, et al., J. Am. Chem. Soc. 2003, 125, 622; Zayats, et al., J. Am. Chem. Soc. 2003, 125, 16006).
In view of the forgoing, it would be desirable to provide a universal detector capable of rapid and universal detection with potential for mass production and deployment. The development of neurotoxin detection systems is crucial for human health and safety in agricultural, domestic, and defense areas.